SULPHUR NUTRITION OF THE CORN PLANT: II. SULPHUR AMIDE-N AND GLUCOSE INTERRELATIONSHIPS

Abstract

Corn (Zea mays L. Dekalb 805) seedlings were grown in culture solutions containing two levels of sulphur - 156.2 LIM S (S) and 6.0 uM (-S). High levels of amide N(0.5-1.2% dry wt. basis) accumulated in the (S) plants. The accumulating amide was asparagine. Only trace amounts of amide-N (-07%) were found in the (+S) plants. In contrast to the amide trend. the glucose level in (+S) plants was very high (3.98%) compared to the trace quantities which were found in the (-S) plants. Thus, there is an inverse relationship between glucose and amides. Exogenous supply of glucose to sulphur deficient plants resulted in increase (88%) in tissue glucose level and this increase was accompanied by a decrease (43%) of amide-N levels in the plants. Also, amelioration of S stress resulted in increase in tissue glucose level and a decrease in amide-N level. Artificial imposition of S stress on sulphur adequate (+S) plants to a drop (53.9%) in glucose level and a concomitant upsurge in amide-N. level, (170%). The above results although clear-out, do not constitute an unequivocal evidence for a cause - effect relationship between glucose and asparagine However, they suggest very strongly that glucose may be functioning as an inhibitor of asparagine synthesis possibly through regulation of asparagine synthetase.